Ignition device and parts thereof



1951 w. c. SMITH 2,575,140

IGNITION DEVICE AND PARTS THEREOF Filed Dec. 29, 1948 k L 62 L94 Z Q 56&/ A?

J4 2 24 75 2a 7 f 2/ (55hm/ZZ 25 w 57 25 an as i 57 Z7 Z6JA/IZEILI/TVOR. BY

Patented Nov. 13, 1951 UNITED STATES PATENT OFFICE IGNITION DEVICE ANDPARTS THEREOF 'Whitfield C. Smith, Oneonta, N. .Y., assignor-to BendixAviation Corporation, New. York, N. Y.- acorporation ofDelawal-eApplication December 29, 1948, Serial No. 67,950

.. 2tClaims. (Cl. 315-57) .This invention relates to ignition apparatuseand' more particularlyto sparkplugs and parts thereof-adapted foruse-in'ignition systems of Qthe-high frequency and' low tensiondistribution ftype employed.for:*igniting the gaseous charges Blthe-cylinders :of internal combustion engines.

-One of-the object of the present invention is -;to provide anoveltransformer unitwhich is :adaptedtoabeaenclosed in a casing of aradio shielded spark .plugiof conventional design, and:pperati-vely-"connected with the center electrode v:Ithere'of.

-=Anothersobject-'of theinvention is to provide atnovelrcombination"oferadio shielded spark plug and;- step-upvoltage-transformer unit whereby g-fIthewdanger'of;ignition :failures-ismaterially reduc'ed.

'-5Stil1---another',objpectof .the invention .is to provide a noveltransformer runit for use ina Ijspark plug or the :like which has a highdegree of e'tliciemzy andaconsumes aminimum of space for iliitscapacity.

A--further objectris to provide a spark plug awhich is'constructed-in anovel manner to give maximum .assurance against the presence of.'moisture and gases which tend' to cause deterioration and electricalfailure.

,A still further-object is to provide novel meansforinsulatlngielectricalparts,-such as the h gh -potential winding of atransformer, against-nearby conductors'whichare at ground or similar lowL potential,-suchas the, shell of a spark plug.

Another object is to providenovelmeans for insuring proper positioningof an insulated trans- 'former unitin-a casing, such-as the-shieldingbarrel of aspark plug.

-I StiILanQtherobject isto'provide novel insulating.meanswhich-willendure the stresses pt-tremendous and sustained vibration under awidely.changing conditions of temperature and pressure.

j -The-above and. further objects and novel {eat tures-r of 9the-presentinvention will. more fully eappear from .the following detaileddescription qwhenthesameis readhinaconnection with theaccompanying.drawings. It is to be expressly understood however, thatthe drawings are for the purpose.of. illustration only and are not in-;tendedsas aedefin-ition vof-the limits ofthe inven- 'tion.

, 4111'; theigdrawings, wherein like reference char- .-';acters refer.to like parts throughout the several views, I Figs;- lrand 2areaendviews of the structure r illustratednin ll'igh 3,; the,same-heing-taken from the'lef-t andrightends,respectively Fig. 3 is alongitudinal sectional view; with some parts shown in full,'of one formof shielded spark plug-transformer combination contemplated by thepresent invention; and

Fig. 4 is a detail view partly insection and with parts broken awayofthe transformer unit of the embodiment of Fig. 3.

ment with a threaded-opening-in anengine cylinder (not shown) A tubularinsulator 12 of rigid ceramic or other suitable insulating material,

' such as aluminum oxide, may be supported in the shell by a tubularwedge 13 of relatively malleable metal, such as copper, or by some othersuitable known means. A center electrode l4, l5 extends through the boreof insulator l2 into spark gap-relation with a so-called groundelectrode l6 secured to shell 10 and said bore may be suitablysealedaround at least a portion of thecenter electrode in any of many wellknown ways. Shell I0 is provided with a metallic radio shieldingbarrel-or-tube I1 which surrounds the projecting end of center electrodeassembly I2,

l4, l5 in'spaced relation thereto andextends beyond the end thereof .toprovide a space or well for receiving a novel transformer unit to benext described.

It is necessary in modern enginesto impress a relatively high voltageacross the points of the spark plugs, and it has been found highlydesirable, in order-toreduce electrical losses and operational failures,to confine the high voltage to the immediate vicinity of the spark plug.To thi 'end, it has been proposed to enclose transformers within theshieldin barrels of conventional shielded spark plugs Much difficultyhas been encountered; however, *in overcoming the many hazards anddifficulties which occur by reason of heat, vibrationandspacelimitations. The novel transformer unit contemplated by this inventionand the novel-manner in which the same is combined-with'and insulatedfrom the spark plugv perse solves theseand other problems in a uniqueand satisfactory manner.

In the ,form illustrated, the step-up transformer or coil is constructedfor easy-installation orreplacement as a self-contained unit in thespark plugshellor barrel l'l. Said-unit comprises an insulator l8 whichis preferablyprovidedwith a shallow recess l9 atoneend and a deepreoesslllattheother. .Avcup or bent strip contact with the inner end 15of the center electrode of the spark plug during installation. Asubstantial portion of the larger or outer recess 20 is preferablyfilled with a metallic core 23 for enhancing the efficiency and capacityof the transformer to reduce losses when a high fre quency source ofelectrical energy is used. Said core may be of powdered metal, such asiron, with a binder of suitable insulating material, such as Bakelite,urea resins, or the like, the same being effective to improve thecoupling between the primary and secondary windings.

The secondary winding 2 f the transformer may consist of a single solidor closely wound layer of insulated wire extending approximately thefull length of insulator [8. In one satisfactory embodiment, 300 turnsof #44 heavy F ormvar insulated magnet wire were used.

' The beginning or low potential end of winding 24 is connected to acontact pin 25, and the high potential end is connected to cap 2| andhence to the center electrode- I5. In order to reduce electrical lossesand the adverse effects of corona to a minimum, this closely or solidendof the barrel. Element 32 may be secured in barrel I! in an air-tightand moisture-proof manner by spot welding or in some other suitablemanner.

Pin 25, which together with element 32 forms the male half of a plug andsocket type electrical connector, extends through a central opening insaid element and the annular space surround ing the pin in said openingis hermetically sealed by a glass-to-metal seal 35 or its equivalent.

The inner end of pin 25 is bent through a slot or opening 36 in the sidewall of insulator l8 for suitable connection to the adjacent ends of 1ywound secondary coil is covered with a highresistanceelectrically-conductive coating (not shown) which may be applied to thewinding by dipping and subsequent drying and baking. Such coating maycomprise finely divided graphite and lamp black suspended in a resinous.base. One suitable formula for the coating material consists of amixture of 10 grams of Acheson Colloids Corp. dispersion #154 (finelydivided graphite suspended in solution with alcohol), 4

7 grams of lamp black, 50 cc. of a solvent such as I mary winding issoldered to contact pin 25 and the other end is electrically connectedto a ring 28 on the lower end of sleeve 26. In one suitable embodimentthe primary winding consisted of 10 turns of #21 Formvar insulatedmagnet wire, the same being preferably wound in the same direction assecondary winding 24.

to provide an automatic transformer hook-up whereby the voltage of theprimary is added to the voltage of the secondary Ring 23, which servesseveral purposes, comprises a central annular portion, a plurality ofprojections 29 that yieldably grin the end of the insulating sleeve, anda plurality of flared resilient projections 30 which engage a shoulder31 on the spark plug shell to rovide a ground connection and springsupport for sleeve 26 to absorb lengthwise toler-i primary winding 27and secondary winding 24.-

Novel means are provided for further insulating the above describedcurrent-carrying elements from barrel I1 and parts connected thereto,said means being adapted to withstand wide variations in temperature andthe shock of sustained vibrations or the like without cracking. In theform shown, several layers of woven fiber glass, which is itself aninsulator, are wound around sleeve 26 and'primary winding 2?. Theselayers preferably extend the full length of said sleeve but may beshorter or longer, if desired. In the completed structure as viewed inFig. 3, the layers 3'! of woven glass fibers are embedded in orimpregnated with a mass of insulating material. which will set to arigid com= pound, but preferably remains a somewhat yieldable andresilient solid. Excellent insularing means are thus provided'whichalsdserve as a mechanical binder and shock absorbing'bub fer for theunit which extends into barrel l'i.

After the completed unit illustrated in Fig."4 is installed in sparkplug barrel H, the structure is thoroughly dried, and the spaces withinthe barrel are evacuated and filled throughan opening 38 with theinsulating material 39in liquid form which will thereafter set as asolid. Preferably, a filling material is used which will set up as asolid through chemical reaction with or without the aid of heat. Thereare several rubber-like compounds of this type now ave-in able, such aspolymerized cashew nut shell-oil mixed with formaldehyde or a styrenepolyester resin. The filling may be effected under vacuum through hole38 which may be laterplugged as shown in Fig. 3. In the interest ofclarity some of the spaces within barrel l! which are filled withcompound 39 are shown with the compound removed. Y

There is thus provided a novel spark plug particularly adapted for usein high frequency and low tension distribution ignition systems forinternal combustion engines, the same being so constructed as to operateefficiently for long periods of time with minimum danger of failure inoperation. Additionally, there'is -pro vided novel insulating meansparticularly adapted for use in the combination of parts disclosed, thesame serving to afford mechanical re-enforcement and supportfor theparts'as well as durable insulation capable of enduring the ri oroustests of your round operation at all altitudes. The novel manner inwhich the parts described have been combined conserves space without acorresponding loss of efficiency or reduction in safety factor. Theconstruction is also such that the coil unit can be removed and replacedif it fails during the useful life of the spark plug per se. y, Althoughonly a single embodiment of the invention has been illustrated anddescribediin 7.6 detail, it is to'be expressly understood that theinvention is not so limited. For example, various other types of sparkplugs which difier specifically in construction from the one illustratedmay be used. Various changes may be made in the design and arrangementof the parts illustrated, as well as in the specific materialssuggested, without departing from the spirit and scope of the invention.

What is claimed is:

1. Ignition apparatus comprising a tubular metallic shell, an insulatedcenter electrode assembly supported in said shell, a tubular metallicbarrel on said shell surrounding and extend ing beyond the end of saidassembly, an end closure for said barrel having a passage therethrough,a contact pin extending through said passage, 2, glass-to-metal seal insaid passage around said pin, an insulated step-up voltage transformerin said barrel comprising a rigid insulator secured to said end closureand having a recess at one end for receiving said pin and a resilientterminal at the other end for electrical engagement with the conductingportion of said assembly, a core of powdered metal with a binding ofinsulating material in said insulator, a secondary winding on saidinsulator comprising a closely wound layer of insulated wire, oppositeends of said winding being electrically connected to said contact pinand said terminal, a high-resistance electrically-conductive coatingcovering said secondary winding, an insulating sleeve surrounding saidwinding and the projecting end of said assembly, a metallic ring mountedon the end of said sleeve and having resilient extensions contactingsaid shell, a space Wound primary winding on said sleeve around saidsecondary winding, opposite ends of said primary winding being connectedto said pin and said ring, a plurality of layers of woven 4 glass fiberssurrounding said primary winding and said sleeve, and a solid yieldableinsulating material filling the remaining space in said barrel andembedding said layers of woven glass fibers.

2. In apparatus of the class described, a tubular metallic barrel havingan internal shoulder, an end closure for said barrel, an electricaltransformer in said barrel comprising a rigid insulator secured to saidend closure, a secondary winding of insulated wire on said insulator, aninsulating tube closely surrounding said winding and engaging anexternal shoulder on said insulator, resilient means under compressioninterposed between said internal shoulder and the end of said tubenearest said internal shoulder, a primary winding on said tube aroundsaid secondary winding, and an insulating mass interposed between saidtube and said barrel comprising a plurality of layers of woveninsulating threads embedded in rubber-like resilient insulation.

WHITFIELD C. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,036,274 Holler Aug. 7, 19362,141,141 Kongsted Dec. 30, 1938 2,414,300 Hamilton Jan. 14, 19472,414,692 Harkness Jan. 21, 1947 2,434,492 Ericksberg et a1. Jan. 2,1948 2,441,047 Wall May 4, 1948 2,461,098 Weatherly Feb. 8, 19492,467,531 Lamphere Apr. 19, 1949 2,482,884 Tognola Sept. 27, 1949 OTHERREFERENCES Fiber Glass Insulation for Magnet Coils, Science News Letter,page 41, July 20, 1946. (Copy in sci. libr.)

